DESCRIPTION: The overall goal of research in the applicant's lab is to determine how neural circuits generate rhythmic behaviors and how these circuits are regulated by neural and hormonal inputs. The applicant proposes to develop a new invertebrate model system, the nudibranch Melibe leonina, and to test the hypothesis that feeding and swimming are both generated by a single multifunctional CPG. This central hypothesis generates four related testable hypotheses which are the focus of the proposal. The first hypothesis is that there is a single, flexible CPG for both swimming and feeding. This will be tested by further analyses of the cellular components and synaptic connections of the swim CPG, to determine the major components of this network. The second hyothesis is that light suppresses both swimming and feeding circuits, explaining why animals are more active at night. This will be tested by direct behavioral measurements to determine whether there is a circadian rhythm in swimming, locomotion and feeding activities, and whether removal of the eyes affects the daily behaviors. The third project is to test the hypothesis is that NO reconfigures the swimming CPG to produce a feeding rhythm. The applicant first proposes to map the distribution of NOS staining in the CNS and periphery. Then a series of experiments are planned in semi-intact animals to prove that NO donors restructure the swim CPG to produce feeding. The fourth project analyzes the same questions from the opposite perspective: do threatening stimuli evoke swimming and suppress feeding by switching a shared CPG to the swim pattern? The applicant will apply the isolated tube feet of a predatory starfish to Melibe skin while recording from swim and feeding interneurons and motor neurons, and determine whether the swimming pattern is evoked in both cell types.